v2.6.4 "___BEACON_ROOT___"

• changed from hard coded https://progenetix.org to template ___BEACON_ROOT___
  in map, schema and configuration files and for handover generation
  • the ___BEACON_ROOT___ is replaced during request processing through the
    detected f"{REQUEST_SCHEME}://{HTTP_HOST}"
• fixed UCSC link generation for BeaconPlus
• removed beaconMap.yaml from schemas, since now part of config/beacon_map.yaml
• renamed ENV to HTTP_HOST for consistency
• new dict_replace_values function in bycon_helpers.py

... and from 2.6.3

• schema file restructuring
  • removed all JSON schemas fromn the source tree since they are generated
    from YAML anyway and changed the file targets in schema_parsing.py to
    .yaml accordingly
  • flattened schema hierarchy structure since there is no need to distinguish
    between src and json directories anymore
  • removed the schemas/bin directory since no json files are generated anymore
  • adjusted documentation generation in markdowner.py accordingly
• cleaned out code w/ removal of "pgxVariant" references since using vrsVariant
  • e.g. in ByconVariant and ByconBundler